Sorry to hear about your situation.
Without knowing the what and how I would have to be a magician to be able to answer your question.
There are so many factors and there are many doors to a website which can potentially be hacked, such as cpanel and
ftp.....not just the wordpress access.
Regarding the AIOWPS plugin, it all depends which features you had activated and how you were using this plugin.
Remember that no security plugin can provide 100% protection against hacking of your site. However, a good security plugin will reduce the chances depending on how it's used.
Our job as security plugin writers and yours as the site owner is to mitigate the risk of being hacked.
Did you at least do the basic security steps when you activated the plugin?
1) change the default "admin" username
2) Choose a strong and secure password
3) Enable login lockdown
Also, did you have the brute force prevention feature active?
With the added security of the secret word, the hacker would've had to have guessed not only the username, but also your password AND the secret word. This would be highly unlikely.
In addition, if you have been careless with your cpanel or FTP credentials then there is nothing that any security plugin can do for you because once someone has access to your files they can do a lot of damage.
So instead of making a blanket statement such as "this plugin was not able to do anything to protect my website" you should at least provide more info about the situation and also do a self assessment of your own security practices - because if one has careless security practices no plugin can protect you, no matter how good it is.